A Fine Synchronization Method for Coherent Fast Frequency Hopping

Coherent fast frequency hopping(CFFH)is attracting growing attention owing to its good antijamming performance and the coherent combining ability.However,compared with the conventional non-coherent fast frequency hopping,CFFH requires a more precise system synchronization.In this paper,we propose a new fine synchronization algorithm for CFFH.This algorithm consists two stages,namely,open-loop stage and closed-loop stage.In the openloop stage,a grid-based search parameter estimation method is proposed.In the closed-loop stage,we construct a fully coherent phase-locked loop(PLL)and a delay-locked loop(DLL)with decoding feedback structure to perform further fine estimation of the system clock skew and time delay,respectively.Moreover,we analyze the effect of the search parameter settings on the estimation error and derive the root mean squared error(RMSE)of estimates in the steady state of the closed-loop stage.Finally,through simulation,the RMSE performance are compared with the corresponding Cramer-Rao low bound(CRLB)and conventional code loop estimation to show the effectiveness of proposed algorithm.

Vanadium-based cathodes for aqueous zinc ion batteries: Structure,mechanism and prospects

As an emerging energy storage device with high-safety aqueous electrolytes, low-cost, environmental benignity and large-reserves, the rechargeable aqueous zinc-ion batteries(AZIBs) have attracted more and more attention. Vanadium-based compounds are also supposed as the potential candidate cathode materials for AZIBs due to their wide variety of phases, variable crystal structures and high theoretical capacity. In this review, the recent progress in the development of vanadium-based materials was summarized,and the relationship between the crystal structure types of active materials and Zn-ion transport mechanism was highlighted. During the charge-discharge process, the different electrostatic repulsion between the cations of vanadium-based compounds with different crystal structures and Zn^(2+)results in a variety of the Zn-ion storage mechanisms, which can be significant guidance for designing the advanced batteryelectrode materials for AZIBs. Furthermore, other factors associated with the storage mechanisms, such as electrolyte components and electrode morphology, are discussed. Finally, the strategies to improve the electrical conductivity, inhibit the dissolution and stabilize the crystal structure of vanadium-based compounds are proposed and the future prospects for developing high-energy-density AZIBs are presented.

Preparation and Characterization of Ag_2S/PMMA Nanocomposites by Microemulsion

Ag2S nanoparticles in polymethyl methacrylate （PMMA） are prepared in n-heptane/sodium bis（2-ethyl- hexyl）sulfosuccinate/water microemulsions. The Ag2S nanoparticles dispersed in the polymer are characterized by FT-IR spectrum, UV-Vis absorption spectroscopy, transmission electron microscopy （TEM）, and X-ray powder diffraction （XRD）. The FT-IR spectrum shows that the composite has the characteristic bands of nano-Ag2S and pure PMMA. The TEM photograph of the sample shows that the Ag2S nanoparticles are elliptical. The phase structure of the composite is characterized by XRD, which reveals that Ag2S particles are formed. The UV-Vis absorption recorded at various times indicates an initial rapid formation of the nanoparticles and the quantum confinement effect of Ag2S nanoparticles.

Panorama of boron nitride nanostructures via lamp ablation

A diverse range of remarkable boron n itride (BN) nano structures subsumi ng nano-homs, nano-rods, nano-platelets, and clusters of hollow nano spheres (nano-onions, arguably of greatest applied and fun damental in terest) have bee n produced exclusively from crystalline BN precursor powder via lamp ablation. The procedure is safe, devoid of toxic reagents, simple, rapid and scalable—generating some genres of nan oparticles that had previously proved elusive. Product structure and composition were unambiguously assessed by high-resoluti on transmission electron microscopy, energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy.